Thermostatic switch

ABSTRACT

There is disclosed a thermostatic switch consisting essentially of a tubular casing formed of a material having a relatively high coefficient of expansion and a circuit controlling member which is disposed therein and formed of a pair of metallic springs having a relatively low coefficient of expansion. This thermostatic switch is provided with means which permits the accurate response to the ambient temperature change i.e., means such as for preventing so called backlash or minute gap caused at the thread-engaging portions between the circuit controlling member and the casing, and it is provided with means which aids in enhancing the heat sensing of the circuit controlling member in co-operation with the sensing of the casing. In another aspect of the invention, there are provided means which can protect the lead wires connected to the circuit controlling member and the temperature adjusting lock screw from erroneous operations caused by inadvertent contact with or impingement on other moving substance such as a body or the like.

United States Patent [191 Kondo [451 Jan. 15, 1974 THERMOSTATIC SWITCHKenshi Kondo, 3-5 Ohkura l-chome, Setagayaku, Tokyo, Japan [22] Filed:Dec. 29, 1972 [21] Appl. No.: 319,522

[76] Inventor:

Primary Examinerl-larold Broome Att0rneyClario Ceccon [57] ABSTRACTThere is disclosed a thermostatic switch consisting essentially of atubular casing formed of a material having a relatively high coefficientof expansion and a circuit controlling member which is disposed thereinand formed of a pair of metallic springs having a relatively lowcoefficient of expansion. This thermostatic switch is provided withmeans which permits the accurate response to the ambient temperaturechange i.e., means such as for preventing so called backlash or minutegap caused at the thread-engaging portions between the circuitcontrolling member and the casing, and it is provided with means whichaids in enhancing the heat sensing of the circuit controlling member incooperation with the sensing of the casing. In another aspect of theinvention, there are provided means which can protect the lead wiresconnected to the circuit controlling member and the temperatureadjusting lock screw from erroneous operations caused by inadvertentcontact with or impingement on other moving substance such as a body orthe like.

5 Claims, 11 Drawing Figures PMENTEDMIB m4 3 786 389 SHEET 3 0F 3 PFIG.IO

THERMOSTATIC SWITCH BACKGROUND OF THE INVENTION This invention relatesto a thermostatic switch which utilizes the difference in thecoefficient of the expansion between two kinds of metals.

A known thermostatic switch of a type disclosed herein consistsessentially of an outer casing formed of a material having a relativelyhigh coefficient of expansion and adapted to directly sense the ambienttemperature change, and of a circuit controlling member disposed thereinand formed, of a pair of metallic springs having a relatively lowcoefficient of expansion. The circuit controlling member usually hasmeans to permit the thread-engagement with one end of the outer casing.More particularly, the circuit controlling member has a studlongitudinally extending therefrom which has a threaded end portion thatin turn is received in an interiorly threaded hole of a sleeve. Thesleeve has an exteriorly threaded outer surface which is inthreadengagement with a threaded hole in one end wall of the casing andusually protrudes outwardly from the end wall of the casing.

Electric lead wires are connected to electric contact members which arecarried on the two opposing spring members respectively and usually aredirected outwardly through the closure of the casing.

Furthermore, there is usually a certain amount of space inside thecasing around the circuit controlling members, which somewhat'retardsthe heat sensing of said controlling member as compared with the sensingof the outer casing.

In a thermostatic switch of a type which has been described above, somedisadvantages are encountered in practical use, such as a. the backlashis likely to take place at threadengagement between said stud and saidsleeve, because, when the ambient temperature is raised, the sleeveportion expands to a greater extent than the stud portion of the circuitcontrolling members, thus causing backlash or a minute gap between theinterior threads of the sleeve and the exterior threads of the studportion, such that there is introduced some degree of delay inresponding to the ambient temperature change; i

b. because of the existence of somewhat excessive space around thecircuit controlling members in the casing, the heat transmission to saidcontrolling members through said casing is somewhat retarded;

c. the lead wires from the electric contact members in the casing to theutside are likely to be subject to inadvertent handling such as beingpulled carelessly, thereby resulting in the erroneous operation of theswitch; and

d. because of the sleeve protruding outwardly from the end wall orclosure of the casing for adjustment of the temperature setting, thereis a risk of the sleeve impinging or contacting some other moving body,thereby resulting in the erroneous operation of the thermostatic switch.

It is accordingly an object of the invention to provide a thermostaticswitch which is substantially free from such backlash at thethread-engaging portions between said stud and the sleeve and betweensaid stud and the end wall of the casing-- It is a further object of theinvention to provide a thermostatic switch which minimizes theretardation of the heat sensing function of the circuit controllingmember with respect to the sensing of the outer casing of the switch.

It is a still further object of the invention to provide a thermostaticswitch which can substantially eliminate the erroneous operation causedby the inadvertent handling of the lead wires.

It is a yet further object of the invention to provide a thermostaticswitch which can substantially reduce the erroneous operation of thethermostatic switch due to the inadvertent handling of the temperaturesetting sleeve.

SUMMARY OF THE INVENTION According to the present invention, there isprovided a thermostatic switch which consists essentially of an outercasing and circuit controlling member as have been described, saidcontrolling members having at one end a stud extending therefrom throughan end wall of the casing to the outside and a compression springmounted at its other end intermediate the other end of the controllingmember and the other end wall of said casing to thereby maintain saidcircuit controlling member in tension, thus precluding the possiblebacklash at the thread-engaging portions between said stud and thesleeve and between said sleeve and the end wall of the casing.

The thermostatic switch further incorporates clamp means mounted on thecircuit controlling member to rigidly secure the lead wires thereto,thus precluding the influence of the external stress which mayinadvertently be exerted from outside, such as by pulling the leadwires.

Still furthermore, the thermostatic switch of the invention features theheat conductive member of a hollow cylindrical form which is provided asa layer of aluminum foil copper foil or the like and it serves as aliner along the inner wall of said casing, thus narrowing the spacebetween the circuit controlling member and the inner wall of the casing,such that the temperature change will be more efficiently transmittedthrough the wall of the casing to the circuit controlling member,presenting improved heat sensing functions between the two.

In addition to these, the thermostatic switch of the present inventionincorporates a locking means adapted to be mounted around saidprotruding sleeve from both sides so as to insure the rigid mounting ofthe stud on the end wall of the casing and to protect the sleeve fromthe influence of external, inadvertent stress application, coupled withthe purpose of providing a consistent temperature setting of the circuitcontrolling member.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a longitudinal elevationalview partially in section of one embodiment of the thermostatic switchof the present invention;

FIG. 2 is a fragmentary perspective view partially broken away of oneend portion of a supporting member for the circuit controlling memberused in the present invention;

FIG. 3 is a transverse cross sectional view taken at points A-A of FIG.1;

FIG. 4 is an exploded perspective view of a locking means for theadjusting screw or temperature setting sleeve of the present invention;

FIG. is a longiutudinal elevational view partially broken away andpartially in section illustrating another feature of the thermostaticswitch of the invention;

FIG. 6 is an enlarged fragmentary sectional view showing thethread-engagement of the sleeve of FIG. 5;

FIG. 7 is a longitudinal elevational view partially in sectionillustrating another feature of the thermostatic switch of the presentinvention;

FIG. 8 is a transverse cross sectional elevational view taken at pointsBB of FIG. 7;

FIG. 9 is a fragmentary perspective view partially in sectionillustrating the lead wires being directed through the holes provided inone end wall or closure of the casing;

FIG. is a longitudinal elevational view partially in section of a stillfurther feature of the thermostatic switch of the present inventionwherein a heat conductive member or liner is mounted along the innerwall of the casing; and

FIG. 11 is a schematic diagram illustrating the principle of thebacklash caused at the points of threadengagement between the stud andthe sleeve, and between the sleeve and the end wall of the casing;

DETAILED DESCRIPTION OF THE INVENTION:

Referring now to FIG. 1 the reference numeral 1 generally designates aheat sensing casing of a tubular form, an end wall or closure 2 and astem portion 3 integral with the end wall. A head 4 is formed on thestem 3 and a compression spring 5 is positioned on the stern beneath thehead. A circuit controlling member 6 is provided and includes a pair ofelectric contact plates 7. Insulating members 8 are wound around themid-portions of the contact plates, said insulating members being madeof a material such as mica. Electric contact mounts 9 and electriccontacts 10 are secured to the plates 7. A supporting member 11 isadapted to support one end of the contact plates 7 and a similarsupporting member 12 is adapted to support the other end of the contactplates 7. A stud or electric contact opening and closing member 13extends through the supporting member 12 and is secured thereto by alocking member such as a nut 14. Notches are provided in the opositesides of the supporting member 12 to receive guide ribs 16 that extendlongitudinally along the inner wall of the casing 1. The stud 13 hasexterior threads 17 that are positioned within the outer end wall orclosure 18 of the casing l in an interiorly threaded hole 19. Atemperature setting or adjusting threaded sleeve or screw 20 which hasan exteriorly threaded portion 21 is adapted to be threaded in thethreaded hole 19. The interior of the sleeve 20 is threaded and isadapted to threadingly receive the exteriorly threaded portion 17 of thestud 13 therein.

The reference numeral 23 designates a pair of tapered holders offrusto-conical shape which is divided into two portions, each having acurved surface of semi-circular cross section. A clamping ring 26 isadapted to fit over the curved, outer surfaces 24 of the frusto-conicalportions 27. Elongated screws 28 are used to urge said frusto-conicalportions against the outer face of the end wall 18. The numerals 29 inFIG. 4 designate holes for receiving the end of the screws 28 therein.

As shown in FIG. 8 lead wires 311 and lead wire clamping members 31 aresecured to the supporting member which has a guide portion 32 having ahole 34 (FIG. 6) of the same diameter as the outer diameter of thesleeve 20. FIG. 6 also illustrates that the end wall is provided with anenlarged annular groove 33. The guide portion 32 extends integrally fromthe end wall or closure 18. Holes 35 (FIG. 9) are provided to pass thelead wires and spiral lead wire guides 36 therethrough.

Referring to FIG. 10, there is shown a heat conductive layer or liner 37mounted along the inner wall of the casing 1, the liner being formed ofmetal foil having high heat conductivity, such as aluminum foil orcopper foil.

In FIG. 11, there is shown a schematic diagram in which the referencenumerals 17 and 21 are the exteriorly threaded portions of the stud 13and the sleeve 20, respectively, while the numerals 22 and 19 are theinteriorly threaded portion of the sleeve 20 and the hole 19,respectively.

FIG. 11 illustrates that there arises a minute gap between the meshingthreaded portions due to the heat influence, i.e., so called backlashphenomenon.

As is now clear from the reading of the description given thus far, thebacklash, which is likely to take place at the points ofthread-engagement between two meshing threaded portions such as thecombination of the threaded portions 17 and 22 and that of 21 and 19, isprevented by the provision of the spring 5 interposed between the head 4and the supporting member 11, said spring being adapted to maintain thecircuit controlling member 6 in tension so as to eliminate such abacklash or minute gap between the meshing threaded portions.

The lead wires 30 are clamped on to the supporting member 12 by means ofthe clamping members 31 so as to block the force being exertedexteriorly, and furthermore the lead wires 30 are protected from wear orrubbing by means of the sprial wire guide 36.

As shown in FIG. 10, because of the provision of the heat conductivelayer 37, the space around the circuit controlling members is lessened,so that the heat transmitted through the wall of the casing (l) isefficiently transmitted through the heat conductive layer 37 inwardly,thus bringing the circuit controlling members into well co-operatedrelation to the outer casing in the sense of the heat sensing orresponding capability.

As shown in FIGS. 1 and 5, the protruding sleeve 20 or temperaturesetting-adjusting screw is embraced from both sides by thefrusto-conical members which 3 are shown as being divided into twoidentical portions as at 23 and 23. The frusto-conical members 23 arereceived in the clamping ring 26 which is pushed towards the end wall 18by means of the elongated screws 28. Accordingly, the threaded sleeve 20is held rigidly against the end wall 18, thus eliminating the centeringdeviation thereof. The sleeve 20 will be further firmly held within thefrusto-conical members 23, if the inner wall of the hole formed in saidfrusto-conical member 23 is knurled. To improve the centering of thesleeve 20 being received in the end wall 18, there is provided anextended sleeve portion or a guide portion 32 as shown in FIG. 6.

As is apparent from the foregoing, the disadvantages experienced withthe conventional type thermostatic switch of a type similar to that ofthe present invention, as referred to earlier under the paragraphs (a)through (d), can be avoided by the provisions of the spring 5, the leadwire clamping members 31, the heat conductive layer 37 and the lockingmeans consisting of frusto-conical members 23, the clamping ring 26 andthe elongated screws 28.

The detailed description of the functions of the known parts of thethermostatic switch are specifically omitted, because these areself-explanatory to those skilled in the art.

It will be understood that this invention is not limited to the detailsgiven herein but that it may be modified within the scope of theappended claims.

What is claimed is:

1. In a thermostatic switch having a tubular casing formed of arelatively high coefficient of expansion material and including aninternally positioned circuit controll-ing member formed of a pair ofmetallic springs having a relatively low coefficient of expansion, leadwire means extend-ing outwardly of said casing from the circuitcontrolling member and means extending outwardly of said casing foradjusting the circuit controlling member, the improvement comprising thecombination of:

a compression spring mounted between one end of the circuit controllingmember and a portion of the casing;

locking means adapted to embrace the externally located portion of theadjusting means, said locking means comprising an axially split,frusto-conical member, a clamping ring positioned over the outer surfaceof said split, frusto-conical member and screws passing through saidclamping ring and threaded into the casing for pulling said splitfrustoconical member together and toward the end wall of the casing; and

means for clamping the lead wire means on the circuit controllingmember.

2. The thermostatic switch as set forth in claim 1 including the furtherimprovement of a heat conductive layer on the interior surface of thecasing.

3. The thermostatic switch as set forth in claim 2 wherein said heatconductive layer is formed of copper foil.

4. The thermostatic switch as set forth in claim 2 wherein said heatconductive layer is formed of aluminum foil.

5. The thermostatic switch as set forth in claim 1 including the furtherimprovement of spiral guide means for protecting the lead wires.

1. In a thermostatic switch having a tubular casing formed of arelatively high coefficient of expansion material and including aninternally positioned circuit controlling member formed of a pair ofmetallic springs having a relatively low coefficient of expansion, leadwire means extending outwardly of said casing from the circuitcontrolling member and means extending outwardly of said casing foradjusting the circuit controlling member, the improvement comprising thecombination of: a compression spring mounted between one end of thecircuit controlling member and a portion of the casing; locking meansadapted to embrace the externally located portion of the adjustingmeans, said locking means comprising an axially split, frusto-conicalmember, a clamping ring positioned over the outer surface of said split,frusto-conical member and screws passing through said clamping ring andthreaded into the casing for pulling said split frusto-conical membertogethEr and toward the end wall of the casing; and means for clampingthe lead wire means on the circuit controlling member.
 2. Thethermostatic switch as set forth in claim 1 including the furtherimprovement of a heat conductive layer on the interior surface of thecasing.
 3. The thermostatic switch as set forth in claim 2 wherein saidheat conductive layer is formed of copper foil.
 4. The thermostaticswitch as set forth in claim 2 wherein said heat conductive layer isformed of aluminum foil.
 5. The thermostatic switch as set forth inclaim 1 including the further improvement of spiral guide means forprotecting the lead wires.